Atlas of Contaminated Sites

Notable case, La Pampa, Puerto Maldonado, Madre de Dios, Peru

Madre de Dios (artisanal gold mining and mercury)

Madre de Dios, minería aurífera (La Pampa)

In the south-eastern Peruvian Amazon, artisanal mining of alluvial gold, which uses mercury to amalgamate the metal, has turned tens of thousands of hectares of forest into bare gravel and thousands of ponds. Mercury turns up in air, fish, birds, people and even in the leaves of intact forest.

Status
Not addressed
Area
52,165 ha on land1
Media
soil, surface water, sediment, air, living organisms
Kind of site
mining
  1. Area. Forest lost to illegal and informal gold mining in the La Pampa area alone between 1985 and 2020: 521.65 km² (Elera-Gonzales et al. 2025, from MapBiomas Perú data). This is a deforested area, not a contamination perimeter; the point on the map marks the department.

Contaminants

Metals

Status

Not addressed

Mining continues. By 2020 the forest lost at La Pampa had reached 521.65 km², growing exponentially since 1985 (Elera-Gonzales et al. 2025). On abandoned land, natural recolonisation and reforestation are being studied at plot scale.

Story

Artisanal and small-scale gold mining is the world's largest anthropogenic source of mercury emissions. In the department of Madre de Dios, one of the most biodiverse regions on Earth, alluvial deposits are dredged and washed and the gold is separated with mercury, which is then burned off. Where primary forest stood there is now a mosaic of gravel piles, bare soil and thousands of abandoned mining ponds, where mercury can be methylated.

In oxbow-lake fish, accumulated mercury depends on the intensity of mining nearby (Barocas et al. 2023); in birds living near mining ponds, feather concentrations are higher (Pisconte et al. 2024). A study of soil and 19 native plant species across five land-cover types, from bare soil to primary forest, found the highest values in the intact forest itself: on average 0.276 mg/kg in the top 5 cm of soil and 0.64 mg/kg in foliage, the highest ever recorded in the region. The authors conclude that the canopy captures mercury from the air and passes it to the soil around the roots (Rodríguez-Pascual et al. 2024).

Abandoned land is slowly recolonised: in a chronosequence of sites left 5, 11 and 23 years earlier, basal area and tree diversity rise with time, but after 23 years the composition is still far from that of the reference forest (Garate-Quispe et al. 2024).

Timeline

  1. 1985Start of the MapBiomas time series of forest loss to gold mining at La Pampa.
  2. 2020Forest lost at La Pampa reaches 521.65 km².
  3. 2024Measurements of mercury in soil and native plants at mining sites are published.

Health

Mercury exposure is widespread in the population: the CONAMAD birth cohort enrolled 198 pregnant women to measure toxic metals and minerals in maternal and cord blood (Berky et al. 2023); in an epigenetic study of adults from the region the high-exposure group had more than 10 µg/g total mercury in hair (Weinhouse et al. 2025).

From the literature

Species that acted on one of this site's contaminants in at least one study. The list is automatic and takes no account of this site's soil, concentrations or climate.

Plants

Fungi

Sources

  1. Rodríguez-Pascual M.J. et al. Hg distribution and accumulation in soil and vegetation in areas impacted by artisanal gold mining in the Southern Amazonian region of Madre de Dios, Peru. Chemosphere, Elsevier, 2024
  2. Elera-Gonzales D.G. et al. Deforestation driven by illegal and informal gold mining in the southern Peruvian Amazon: a predictive land use analysis over the next 50 years. Environmental Monitoring and Assessment, Springer, 2025
  3. Garate-Quispe J. et al. Changes in floristic and vegetation structure in a chronosequence of abandoned gold-mining lands in a tropical Amazon forest. Heliyon, Elsevier, 2024
  4. Barocas A. et al. Local intensity of artisanal gold mining drives mercury accumulation in neotropical oxbow lake fishes. Science of the Total Environment, Elsevier, 2023
  5. Pisconte J.N. et al. Elevated mercury exposure in bird communities inhabiting Artisanal and Small-Scale Gold Mining landscapes of the southeastern Peruvian Amazon. Ecotoxicology, Springer, 2024
  6. Berky A.J. et al. In Utero Exposure to Metals and Birth Outcomes in an Artisanal and Small-Scale Gold Mining Birth Cohort in Madre de Dios, Peru. Environmental Health Perspectives, NIEHS, 2023
  7. Weinhouse C. et al. High exposure variance enables candidate biomarker detection in a small EWAS of methylmercury-exposed Peruvian adults. BMC Genomic Data, BioMed Central, 2025
  8. Department of Madre de Dios (coordinate), Wikipedia (en), 2026

Draft compiled from public sources, not yet reviewed.